This invention relates to magnetic tape cartridges of the belt driven type, for example as shown in U.S. Pat. No. 3,692,255 issued to Von Behren. These cartridges require a drive belt which presses against the supply and take-up rolls of magnetic tape to move the tape from one roll past a read/write mechanism, when inserted in a drive, and onto a second roll. The drive belt extends around a drive roller and guide rollers, also referred to as corner rollers, while simultaneously engaging the magnetic tape rolls. Tape tension is desirable to facilitate contact with a read/write head and to improve overall performance of the tape cartridge.
Various means for providing belt drag or tape tension in magnetic tape cartridges have been disclosed. For example, one reference discloses a friction brake shoe across which a drive belt must pass to apply drag to the belt. Another reference describes the use of guide rollers rotating on shafts in which the shafts and the guide rollers are constructed of materials which produce a predetermined amount of friction or drag. It is also known to use a similar technique in which the guide rollers have a compressible rubber core and a rigid peripheral portion which function to provide a small drag to each roller. Other means of creating drag comprises use of a bowed rotating elastomeric washer, or a washer backed with a spring to the axis of the roller. Use of molded plastic guide rollers each having a coil spring formed integrally with the guide roller is also disclosed. A drawback to these constructions is the characteristic of plastic springs to experience creep and stress relaxation under load during the product's life cycle. The product will then exhibit tape tension variation and so lead to product failure.